Method of protection of metal surfaces from corrosion

ABSTRACT

The present invention is a method of protecting metal surfaces from corrosion which comprises contacting the metal with an organo phosphonic, phosphonous or phosphinic acid.

United States Patent Donald L. Schmidt;

William J. Leahy, both of Midland, Mich. 824,246

May 13, 1969 Dec. 28, 1971 The Dow Chemical Company Midland, Mich.

inventors Appl. No. Filed Patented Assignee METHOD OF PROTECTION OF METAL SURFACES FROM CORROSION 8 Claims, No Drawings U.S. Cl l48/6.15 R, 106/14, 252/389 Int. Cl C23! 7/00 Field 01 Search 148/615;

Faulkner, .1. Oil Col. Chem. Assn., 1967 Vol. 50 pp. 524, 525, 526, 541, 542, 544

Primary Examiner-Ralph S. Kendall Attorneys-Griswold and Burdick, William R. Norris and Lloyd S. Jowanovitz ABSTRACT: The present invention is a method of protecting metal surfaces from corrosion which comprises contacting the metal with an organo phosphonic, phosphonous or phosphinic acid.

METHOD OF PROTECTION OF METAL SURFACES FROM CORROSION BACKGROUND OF THE INVENTION inhibition of the process is provided by formation of a hydroly sis resistant MO-P bond between the metal and the acid, thus setting up a layer of organic moieties of the acid on the metal surface. The layer effectively keeps water and water- Thi metal Surfaces are reactive and require protection 5 borne corrosives out of contact with the metal surface. The' from water corrosion and waterborne corrosive agents. The pihtehhoh ihoiehjses as the length of the carbon chain of h surface of plastic which has been coated with a thin metal is organic moiety .ihcrehses' h i f h as the chrhhh Chhlh especially susceptible to corrosion. Aluminum has been found becomes hxceedihgiy iohg ihhihihoh h chiiosioh hecoihes to be an effective coating for polyester plastic films. However, i effective and aiess Protective homing is provided Acids the aforementioned difficulties are quite apparent when aluin which the organic moiety chhthihs h one to about 24 minum is applied to the polyester film in very thin layers. caihoh atoms are P h Acihs having 10 to i4 carhoh Present methods of protecting such films include anodization htohis in h organic moieiiy provide especially effective and overlacquering or laminating the aluminum Surface with a tectlon, with the aclds havlng 12 carbon atoms being the most tough corrosion resistant plastic. 15 preferred It is known that phosphoric acid may be used to form a cor- Phosphohie acids have been tieuhd to Provide Protection rosion resistant coating on metal surfaces. This method of Perior to that of the Phosphihie and Phosphohous acid and are coating metal Surfaces commonly known as parka-hing, the preferred acids for the practice of the present invention. volves coating the metal by dipping or spraying it with a solu- The Orgahie moiety y be Substituted Substitutedtion of phosphoric acid. The process is normally used to prosubstitutehts which ay form a P of theorgahie moiety are tect massive forms of metal and coatings having a thickness of Preferably those Whleh do not slghlfieahtly decrease from 0.000l5 to 0.0003 inch are normally applied to effecy p y- Fluorihei chlorine, bromine 'y are tively protect the metal substrate. Such a method would not be PrefeTredother Substituehts include y i mereapto and readily applicable to thin metal films due to the excessive y y p thiekhess of e coating The PmeeSS also p y reagents The invention is normally practices by practiced a dilute which would smp the Polyester film of its aluminum ssolution of the acid to be applied and dipping the metal into it.

a 3135 i 7558 teaches the use ofa PhOSPhQhate ih Polar organic liquids such as acetone, tetrahydrofuran and the comhihahoh with a deieigehcy buiidei' This composition is lower ethers, i.e., those ethers containing from two to 10 cartaught to have the effect of reducing the cori'osivehess of the hon atoms, are convenient solvents for the acids used in the detergency builder by the in situ formation of a protective present method water and nonpolar organic Solvents may coming the metai surface and is mended for use in aqhe' also be used although the acids are somewhat less soluble in ous solutlon wherein the acid salt acts as the corrosion inhibithese Solvents. w water is emp|oyed as the Solvent, the PH of the solution should be less than 7. A dipping period of from It would be deslrable and it is an ob ect of the present lnvenabout 10 to 15 Seconds is Sufficiem to impart a protective tion to provide a method for inhibiting corrosion of metal surcoating to the memL Repeated dipping may be employed to provide a more substantial protective coating. The coated h h hmhhi: ohiect provide Such a meihhd ,which h metal may then be washed with the solvent and allowed to dry. :sggh be carried out whhoht the use of Specihhzed equip The metal may be contacted with the acid solution by other means such as spraying, brushing or roll coating. The protecbeast films by lntroduclng the acld to a fluld contained in a metal vessel.

' By such addition, the sides of the vessel will be protected from SUMMARY OF THE INVENTION corrosion- The method can be used to coat an of the metals which The present lhvehhoh h methhd for phhechhg metal form insoluble phosphates. The comm n construction metals faces h applying pmthchve Cohhhgs metal shrfhces' The such as iron. nickel, copper, zinc, lead, tin, magnesium, and method involves contacting the metal with a solutlon of an aIuminum may be coated by the present method. The method it o o is especially effective for coating thin sheets of aluminum. (R3 on) phosphonic (R son r phosphonous (Rt 0) acid The following examples will serve to more fully illustrate the l present lnventlon. OH H The R group attached to the acid radical is a hydrophobic or- EXAMPLES i 9 gahie moiety having one to about 24 Carbon atoms- Solutions of acids were prepared by dissolving 0.1 gram of ampleS of R g p are a Straight branched chain the acid in 100 milliliters of solvent, Examples 1-5 used i h or unsubstituted y i 'y aikaryi or arylaikyi tetrahydrofuran and examples 6-9 used acetone as the soltalhlhg from one to abl1t24 vent. Aluminum coated polyethylene terephthalate film was Unexpectedly the aeid is h e p the acid Salts of dipped into the solution for a period of from about 10 to 15 i 8 in providing coiiosioh proiechoh to seconds. In each case the film was cut in half before treatment meiiii surfaces especiahy meiai surfaces which i'eadiiy form with the acid solution and one-half left untreated as a control. oxide surface coatings. Particularly useful results are achieved After the m which had been treated was allowed to dry and in the instance of thin meiai himswashed with acetone to remove unreacted acid, it and the con- DESCRIPTION OF PREFERRED EMBODIMENTS trol sample were immersed in boiling deionized water and the time requlred for removal of the metal coating was vlsually ob- While the present invention is not premised on an explanaserved. Table i represents the results of these tests for a tion of its underlying theory, it is believed that the corrosion number of acids.

TABLE I Time required to Ex. Demetalizo Demvtalizo No. Acid Formula treated him untreated film 0 1. Methyl phospllonic acid CH3? e011 1 mill. 4?. sue. 1 mill. 3 sec.

Me -ll.-

Ex. \o \t'ill l mmul l 2 lhi-nyl phosphonic acid. sllsl ()lI ,2 3 n-Octyl phosphonic acid (tllni (HI 4 ll-l)(lll\l' \l I phosphonic acid (nligs l (i ll 5 li-(irtadvcvl phosphonic acid ('nlla: l (HI l) ll U ti ()ctyl phosphinic acid ltslliml Ull 0 T 3.3.3-1rillum'opropyl phosphinic acid F11 Hit-l: l U l[ ll a lhvni'l phosphonous arid. y I 1) ll U 7 .I ||-l )orll'ryl l phosphonic acid (r ll '5 l 0 ll 'limo required to lhmv-tzilizt lhmctulizt' trvatvil lilm untreated lilni l min. 12 si'v l min. 3 sec.

min. 7 sec 1 min. 15sec.

16 111111.!) svc 1min. 3 t(.

15 min. 0 S 1 min. 3 svc.

l min. Stt 54 sec,

1 min. 30 sec. 54 sec.

1 min. 5N SI(' 54 sec.

16 min. l S l. 36 set.

I Whvn dodecyl phosphonic acid was usml, no (li'nwliilization had occurred in 16 minutes, at which Linn this-xpl-rinulit was stopped.

EXAMPLES lO-l 3 In order to compare the elTectiveness of the present method, wherein the solvent was either aqueous or nonaqueous, and the method of providing protection by using the aqueous solution of the acid salt, the following experiment was conducted:

A piece of aluminum coated polyethylene terephthalate film was cut into four pieces. The pieces were designated A, B, C and D and treated as follows:

10. A was dipped in a solution of 0.1 gram dodecyl phosphonic acid in 100 milliliters of acetone for 30 seconds.

I l. B was dipped in a solution of 0. 1 gram of the sodium salt of dodecyl phosphonic acid in 100 milliliters of boiling water for 30 seconds.

12. C was dipped in a solution of 0.l gram of dodecyl phosphonic acid in 100 milliliters of water for 30 seconds. The water was heated to its boiling point in order to get the acid into solution.

13. D was left untreated and used as a control.

Each of the treated samples was washed with the acid solvent and allowed to dry after treatment. Each sample was dipped into boiling deionized water and the time required for the metal coating to be removed was visually observed. Table ll represents the results of these tests.

The above data indicate that the sample treated with a 75 nonaqucous solution of the acid took more than twice as long to demetalize than did that treated with a water solution of the acid. The acid salt imparted some protection to the metal surface but considerably less than did the unaltered acid.

In a manner similar to that of examples l and ll protective coatings can be applied to the surfaces of metals other than aluminum, such as for example. iron, nickel, copper, zinc, lead, tin or magnesium.

The invention is practiced in a manner similar to that of the above examples wherein the acid employed is characterized of the formula and R is straight or branched chain, substituted or unsubstituted, pentyl, heptyl, nonyl, undecyl, tridecyl, pentadecyl, nonadecyl, docosyl and tetracosyl. However, R is selected so that the total number of carbon atoms in the molecule does not exceed about 24.

Specific examples of such acids are n-pentyl phosphonic acid, (p-t-butylstyryl) phosphonic acid, hexyl phosphonic acid, n-heptyl phosphonic acid, 3-heptyl phosphonic acid, octyl phosphonic acid, n-nonyl phosphonic acid 4-nonyl phosphonic acid, n-undecyl phosphonic acid, n-pentadecyl phosphonic acid, n-nonadecyl phosphonic acid, n-tetracosyl phosphonic acid, dipentyl phosphinic acid, heptyl butyl phosphinic acid, dinonyl phosphinic acid, benzyl butyl phosphinic acid, benzyl heptyl phosphinic acid, benzyl hexyl phosphinic acid, dibenzyl phosphonic acid, di-n-butyl phosphinic acid, diundecyl phosphonic acid, didocyl phosphinic acid, dihexyl phosphinic acid, di-n-octyl phosphinic acid, bis(2-ethyl hexyl) phosphinic acid, butyl phenyl phosphinic acid, decyl ethyl phosphinic acid, di-t-butyl phosphinic acid, didecyl phosphinic acid, diisobutyl phosphinic acid, diisopropyl phosphinic acid, di-n-propyl phosphinic acid, ethyl isopropyl phosphinic acid, isopropyl phenyl phosphinic acid, n-pentyl phosphonous acid, 6-undecyl phosphonous acid, n-tridecyl phosphonous l. A method for protecting thin metal films not adaptable to treatment with phosphoric acid from corrosion which comprises contacting the metal film with a polar organic liquid solution of an acid characterized by the formula wherein R is a straight or branched chain, hydrophobic, substttuted or unsubstituted alkyl, aryl, alkaryl or arylalkyl group containing from to l4 carbon atoms; thereby setting up a layer of organic moieties of the acid on the metal surface.

2. The method of claim 1 wherein R is an alkyl containing from 10 to 14 carbon atoms.

3. The method of claim 2 wherein the acid is characterized by the formula CERTIFICATE OF CORRECTION Patent No. 3,630,790 Dated 28 December 1971 In fl Donald L. Schmidt and William J. Leahy It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line &7, insert organo phosphinic at the end of the line following "an"; line 57 insert -ca.rbonbetween "2h" and "atoms."-

Column 2, line 25, delete practices by" and insert -by preparing-- between "practiced" and "a dilute".

Column l, line +6, delete "of" and insert -by-; in the blank space between lines k8 and 53 insert the following formulae:

Column l, line 76, insert the following after the last word in the column, "phosphonous" acid, lO-nonadecyl phosphonous acid, n-docosyl phosphonous I acid, and n-tetracosyl phosphonous acid.

Signed and sea-led this 27th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents P0405) Q UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3,630,790 Dated 28 December 1971 Inventorv(s) Donald L. Schmidt and William Leahy It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line &7, insert organo phosphinicat the end ofthe line following "an"; line 5? insert --carbonbetween "2 and "atoms."

Column 2, line 25 delete "practices by" and insert by preparing-- between "practiced" and "a dilute".

Column l, line L6, delete "of" and insert -;by--; in the blank space between lines &8 and 53 insert the following formulae:

Column line 76, insert the'following after the last word in the column, "phosphonous":

- acid, lO-nonadecyl phosphonous acid, n-docosyl phosphonous acid, and n-tetracosyl phosphonous acid.

Signed and sealed this 27th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOT'ISCHALK Attesting Officer Commissioner of Patents 

2. THe method of claim 1 wherein R is an alkyl containing from 10 to 14 carbon atoms.
 3. The method of claim 2 wherein the acid is characterized by the formula
 4. The method of claim 3 wherein R is an alkyl containing 12 carbon atoms.
 5. The method of claim 1 wherein the solvent is acetone, tetrahydrofuran or a lower ether.
 6. The method of claim 1 wherein the metal is selected from the group consisting of iron, nickel, copper, zinc, lead, tin, magnesium or aluminum.
 7. The method of claim 1 wherein the metal is dipped into the acid solution, rinsed with the acid solvent and allowed to dry.
 8. The method of claim 1 wherein the metal film is aluminum. 